New Branch Office Installation (no SBS?)

Hi,
I am doing an installation at a branch office on the West Coast for a company headquartered on the East Coast. The branch office will only have 5 people working there within the next couple of years so it will be small. I am putting together a quote for hardware/software that they will need in order to run this office. I'm trying to justify purchasing a server for them. Could you please give my your opinions on the following issues and let me know your advice?

1) As this is a branch office, with a headquarters on the East Coast, it would sort of useless to install SBS 2003 at this office since SBS has to be the DC. --am I think about this the right way? I would love to install SBS here because the office is so small, but the fact that SBS won't authenticate with their main domain makes this option a no-no, correct?

2) If I can set up the branch office users to use Outlook/Exchange via RPC over HTTPS (to communicate with HQ) then would I need to install Exchange locally at the branch office?

3) The branch office users mainly want these two things: To be able to use Outlook to connect to Exchange as if they were in the domain (they don't want to use OWA). And also to use SalesLogix in the branch office which is installed at HQ.

1, correct, you cannot use SBS
2, no, if you use RPC/HTTPs - you will not need a local server (this would be my preferred option)
3, what does saleslogix need? can you use a VPN to access the main server? do you need to??

why not have them on a site-to-site vpn so they can use exchange via MAPI (what exchange usually uses)? Then their PC could join the domain and be 'on the network' of the main office. Their PCs would be setup just as the main office pcs (different gateway of course).